Red Hat Bugzilla – Bug 429604
[PATCH] udev rules to automatically assemble devices
Last modified: 2014-03-16 23:12:05 EDT
Description of problem: The attached udev rules (70-mdadm.rules) allow for automatic assembly of RAID devices on insertion. It means we can get rid of always running mdadm on boot. Not sure whether these should go in mdadm or udev proper. I suppose udev already has 64-md-raid.rules, but I could see packaging these rules with mdadm (it's not like they're going to work without it.) Version-Release number of selected component (if applicable): udev-118-1.fc9 mdadm-2.6.4-1.fc8
Created attachment 292417 [details] rules that incrementally assemble arrays on insertion
mdadm would be fine, so that I can remove 64-md-raid.rules
64-md-raid.rules is different; that's for persistent paths. These rules are for actually getting them activated.
Added in 2.6.4-3.fc9.
This is a nice approach. Unfortunately it's not working for me on a fully updated rawhide system; I have to manually run 'mdadm --assemble --scan' to start my array (using the old config file). What log files / information do you need?
Here's some info My old config file [root@hook ~]# cat /etc/mdadm.conf DEVICE /dev/disk/by-id/scsi-SATA_WDC_WD5000AAJS-_WD-WCAPW0295169 DEVICE /dev/disk/by-id/scsi-SATA_WDC_WD5000AAJS-_WD-WCAPW0594845 DEVICE /dev/disk/by-id/scsi-SATA_WDC_WD5000AAKS-_WD-WCAPW0493929 DEVICE /dev/disk/by-id/scsi-SATA_WDC_WD5000KS-00_WD-WCANU1914880 DEVICE /dev/disk/by-id/scsi-SATA_WDC_WD5000KS-00_WD-WCANU2209762 ARRAY /dev/Fusion500P uuid=c5fc394c:f33279ab:7630b1ba:099a5109 auto=md These are unpartitioned disks [root@hook ~]# ls -l /dev/disk/by-id/scsi-SATA_WDC_WD5000* lrwxrwxrwx 1 root root 9 2008-02-23 17:44 /dev/disk/by-id/scsi-SATA_WDC_WD5000AAJS-_WD-WCAPW0295169 -> ../../sdb lrwxrwxrwx 1 root root 9 2008-02-23 17:44 /dev/disk/by-id/scsi-SATA_WDC_WD5000AAJS-_WD-WCAPW0594845 -> ../../sdi lrwxrwxrwx 1 root root 9 2008-02-23 17:44 /dev/disk/by-id/scsi-SATA_WDC_WD5000AAKS-_WD-WCAPW0493929 -> ../../sdk lrwxrwxrwx 1 root root 9 2008-02-23 17:44 /dev/disk/by-id/scsi-SATA_WDC_WD5000KS-00_WD-WCANU1914880 -> ../../sdh lrwxrwxrwx 1 root root 9 2008-02-23 17:44 /dev/disk/by-id/scsi-SATA_WDC_WD5000KS-00_WD-WCANU2209762 -> ../../sdj That all all raid members, here's one of them [root@hook ~]# /lib/udev/vol_id /dev/sdk ID_FS_USAGE=raid ID_FS_TYPE=linux_raid_member ID_FS_VERSION=0.90.0 ID_FS_UUID=c5fc394c:f33279ab:7630b1ba:099a5109 ID_FS_UUID_ENC=c5fc394c:f33279ab:7630b1ba:099a5109 ID_FS_LABEL= ID_FS_LABEL_ENC= ID_FS_LABEL_SAFE= However [root@hook ~]# udevinfo --query all --name /dev/sdk P: /devices/pci0000:00/0000:00:09.0/host9/target9:0:0/9:0:0:0/block/sdk N: sdk S: disk/by-id/scsi-SATA_WDC_WD5000AAKS-_WD-WCAPW0493929 S: disk/by-id/ata-WDC_WD5000AAKS-00TMA0_WD-WCAPW0493929 S: disk/by-path/pci-0000:00:09.0-scsi-3:0:0:0 E: ID_VENDOR=ATA E: ID_MODEL=WDC_WD5000AAKS-0 E: ID_REVISION=12.0 E: ID_SERIAL=SATA_WDC_WD5000AAKS-_WD-WCAPW0493929 E: ID_SERIAL_SHORT=WD-WCAPW0493929 E: ID_TYPE=disk E: ID_BUS=scsi E: ID_ATA_COMPAT=WDC_WD5000AAKS-00TMA0_WD-WCAPW0493929 E: ID_PATH=pci-0000:00:09.0-scsi-3:0:0:0 So it seems like udev isn't running vol_id on unpartitioned disks. That's probably a bug. Adding upstream udev maintainer to the Cc. Kay?
Also, two things 1. the homehost feature in mdadm is pretty broken - some attempt to protect the user against himself; As such, we should disable it as it will break hotplugging arrays. With hotpluggable buses such as USB, Firewire, eSATA this is important. Myself? I have a 5-disk tower using RAID5 that I happily plug into different machines all the time. With /etc/mdadm.conf this worked great (using /dev/disk/* persistant symlinks), now it's broken. 2. at the same time we need a way for e.g. a forensic live cd (one used to inspect a system without touching it) to disable things like autoassembly. There should probably be a boot option e.g. 'noassembly'. 70-mdadm.rules should then check this and avoid assembly if it's set. Similar, in the future LVM assembly should check the same variable.
True: ENV{DEVTYPE}=="partition", IMPORT{program}="vol_id --export $tempnode" We can't run it, because of missing events for media changes. The next kernel should have it: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=285e9670d91cdeb6b6693729950339cb45410fdc but during the merge, seems something broke it, at least I don't see events the now. I need to find out, how fix it. Then we can call vol_id, and properly update the values/symlinks at media changes.
(In reply to comment #8) > True: > ENV{DEVTYPE}=="partition", IMPORT{program}="vol_id --export $tempnode" > We can't run it, because of missing events for media changes. Presumably we can run this if removable==0 yes? Might be a good interim fix, at least as a vendor patch. > The next kernel should have it: > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=285e9670d91cdeb6b6693729950339cb45410fdc > > but during the merge, seems something broke it, at least I don't see events the > now. I need to find out, how fix it. Then we can call vol_id, and properly > update the values/symlinks at media changes. Sounds good this will get fixed properly in the shiny future. Thanks.
(In reply to comment #7) > Also, two things > > 1. the homehost feature in mdadm is pretty broken - some attempt to protect the > user against himself; As such, we should disable it as it will break hotplugging > arrays. With hotpluggable buses such as USB, Firewire, eSATA this is important. > Myself? I have a 5-disk tower using RAID5 that I happily plug into different > machines all the time. With /etc/mdadm.conf this worked great (using /dev/disk/* > persistant symlinks), now it's broken. Is the conf file still around when this is failing? > 2. at the same time we need a way for e.g. a forensic live cd (one used to > inspect a system without touching it) to disable things like autoassembly. There > should probably be a boot option e.g. 'noassembly'. 70-mdadm.rules should then > check this and avoid assembly if it's set. Similar, in the future LVM assembly > should check the same variable. If the livecd doesn't have a mdadm.conf, I don't *think* anything will be assembled.
(In reply to comment #10) > Is the conf file still around when this is failing? It fails both when the config file is present and when it's gone. > If the livecd doesn't have a mdadm.conf, I don't *think* anything will be assembled. The point is that we want hotplug of RAID arrays to Just Work(tm).
The discussion with upstream (which admittedly happened outside of this bug) was that they did not want auto-assembly of arrays that were not related at least in some way to the system (whether via config file or homehost (but not both)). This is due to concerns they have about 1) array name collisions (what happens when you have multiple arrays whose superblocks claim to be md0) 2) fiber devices on a SAN which could be seen by mutliple machines. #1 probably needs tested to see what we do now. #2 seems like it's a bug if you configure your SAN that way.
So I partitioned the components of my array. Now I'm running into this. # /sbin/mdadm --incremental /dev/sdg1 mdadm: failed to open /dev/md/d0: No such file or directory. So I played around # mkdir /dev/md # ln -s /dev/md0 /dev/md/d0 # ls -l /dev/md/d0 lrwxrwxrwx 1 root root 8 2008-03-17 22:36 /dev/md/d0 -> /dev/md0 # /sbin/mdadm --incremental /dev/sdb1 mdadm: failed to open /dev/md/d0: File exists. Hmm... # rm -f /dev/md/d0 And now # /sbin/mdadm --incremental /dev/sdb1 mdadm: /dev/sdb1 attached to /dev/md/d0, not enough to start (1). # /sbin/mdadm --incremental /dev/sdg1 mdadm: /dev/sdg1 attached to /dev/md/d0, not enough to start (2). # /sbin/mdadm --incremental /dev/sdh1 mdadm: /dev/sdh1 attached to /dev/md/d0, not enough to start (3). # /sbin/mdadm --incremental /dev/sdi1 mdadm: /dev/sdi1 attached to /dev/md/d0, not enough to start safely. # /sbin/mdadm --incremental /dev/sdj1 mdadm: /dev/sdj1 attached to /dev/md/d0, which has been started. So mdadm needs the directory /dev/md to exist. It needs to be empty too. Btw. # ls -l /dev/md/d0 brw------- 1 root root 254, 0 2008-03-17 22:37 /dev/md/d0 # udevinfo -q all --name /dev/md/d0 node name not found Sigh. It's 2008 and we still have things like mdadm creating it's own device nodes. That's just not maintainable. (Of course ironically it refuses to create _directories_). # rpm -q udev mdadm udev-118-5.fc9.x86_64 mdadm-2.6.4-3.fc9.x86_64
Talking to notting on IRC we decided the course of action right now is to patch mdadm so it creates the /dev/md/ directory if it's not there. Doug, can you look into this? Thanks.
I'm a bit confused as to what the status is here. Is the feature in, but broken, or is the feature not in yet? Should we have a new bug for the brokenness and close thins one out? Help me out here guys, time on Fedora 9 is ticking away.
Yes, someone needs to spend a few seconds making the mdadm package provide the /lib/udev/devices/dm directory. Then this bug will go away.
I'm confused. Why that directory instead of /dev/md?
Oh, I meant /lib/udev/devices/md .. md.. not dm. I always mix it up.
(In reply to comment #16) > Yes, someone needs to spend a few seconds making the mdadm package provide the > /lib/udev/devices/dm directory. Then this bug will go away. Of course /sbin/start_udev will start complaining that this is "deprecated" but see bug 440962. Can we add this? Thanks.
Please try the packages from: http://koji.fedoraproject.org/koji/taskinfo?taskID=569782
Built as 2.6.4-4.fc9.